Sea urchin sperm undergo the acrosome reaction when contacting the jelly layer of the egg. This releases the acrosome process which is coated with the egg-binding protein. The egg-binding protein binds the sperm to glycoprotein receptors on the vitelline envelope of the egg. The acrosome process penetrates the vitelline envelope and the plasma membranes of the sperm and egg fuse. The sperm is then drawn into the egg cytoplasm. Exocytosis of egg cortical granules occurs releasing enzymes which destroy supernumerary sperm-egg bonds. We are isolating and characterizing the components of egg jelly which cause the acrosome reaction. We will isolate the jelly receptor sites from the sperm plasma membrane. The interaction of jelly component with its receptor will be studied in detail to explain the species specific mechanism of the acrosome reaction. We have isolated the sperm acrosome vesicle containing the egg-binding protein which we have named bindin. We will completely characterize bindin through determination of its amino acid sequence. We have isolated the vitelline envelope and its major glycoprotein component and propose to completely characterize it. We will study the interaction of bindin and this glycoprotein from several species to determine the molecular basis for species specific sperm-egg binding. Because sperm-egg binding also occurs during mammalian fertilization we propose to isolate hamster bindin. We will immunize female hamsters with pure bindin in an attempt to achieve highly specific immuno-sterility which avoids autoimmune complications. We believe this research will lead to the development of novel methods of non-hormonal contraception.